In a modern wind turbine, a nacelle is a more or less rectangular housing adapted to be positioned on top of a wind turbine tower and finally to house and cover elements such as main bearings, a main shaft, a gearbox, a generator and a supporting structure for such elements. In some wind turbine constructions, one or more of the mentioned elements, such as the gearbox, may not be needed. When a wind turbine is assembled on a site, the nacelle is positioned on top of the wind turbine tower by connecting the supporting structure or intermediate elements such as a yaw bearing of the nacelle with the tower.
During and after production of the nacelle, the nacelle has to be handled a number of times. It is necessary to move the nacelle one or more times, such as in the following situations; within the production facility, from the production facility to a storage facility, from the storage facility to a transport device, from the transport device to another intermediate transport or storage device, and from a final transport device or even from a position on the ground at an erection site and to its final position on top of the wind turbine tower.
Typical length, height and width of the nacelle are around 15000 mm×4000 mm×3300 mm. A typical weight of the wind turbine nacelle is in the interval of 50 to 150 tons, among others depending on the size of the wind turbine for which the nacelle is provided and the materials used for the nacelle.
When handling the nacelle in a plurality of situations as described, it is of utmost importance that handling takes place as safely as possible for personnel and for the nacelle itself. Furthermore, it is of utmost importance that handling the nacelle can be carried out rapidly and precisely.
A way of handling a nacelle is to attach soft slings to lifting points of the nacelle. The nacelle is subsequently lifted by a crane or the like by pulling the soft slings.
The inventors of the present invention have found that known solutions, at least to some extent, fail to provide either a safe handling of the nacelle or a fast or precise handling of the nacelle. Attempts to succeed in providing one or more of these factors have often led to a decrease of an ability to succeed in providing one or more of the other factors. It has also been seen that known solutions increase the cost of the handling devices or that they decrease the flexibility of how to handle the nacelle to a level which is not satisfactory to the wind turbine companies or the companies handling the nacelle. In consequence, the present invention is provided.